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From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple2
Subject: Re: RAMFast SCSI
Message-ID: <1990Oct21.072033.4702@nntp-server.caltech.edu>
Date: 21 Oct 90 07:20:33 GMT
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scottr@gnh-applesauce.cts.com (Scott Rothstein) writes:

>Apple's DMA SCSI simply transfers the accessed data directly to RAM, hence the
>speed (and the Direct Memory Access name). The RAMfast does this, plus
>1)  has its own 10 MHz processor

The speed of the CPU is not very important, what's important is that it is
a coprocessor and can run at full speed in the background while the computer
does its own thing and sends the coprocessor commands when it needs something.

>2)  a lookahead cache that stores the next 7 bytes

The lookahead feature is made possible by the coprocessor, you can set it from
0 to 60K for each partition; it generally helps when you are copying lots of
little files.

Todd Whitesel
toddpw @ tybalt.caltech.edu